Prepared by the Marine Species Section
Approvals and Wildlife Division, Environment Australia
in consultation with the Marine Turtle Recovery Team
 
  July 2003


 
  Download Recovery Plan for Marine Turtles in Australia - PDF (marine-turtles.pdf - 567 KB)
from pages #23 & #33
 
  Dangers to Turtles  
  Boat Strike  
  Marine turtle mortality due to boat strike has been identified as an issue in Queensland waters, principally in Moreton Bay and Hervey Bay. The need to restrict boat speed in areas of important marine turtle habitat is identified (Table 12) and opportunities for awareness raising and educative activities with boat users should be utilised.

 
  Seagrass Feeding Habitat  
  Seagrass communities are essential habitats for several marine turtles but particularly green turtles. Tropical and subtropical Australia is one of the richest areas in the world with respect to seagrasses. Despite the extensive area and species diversity of seagrasses, there have been reports of declines in seagrasses in tropical and sub-tropical Australia. Changes in seagrass occur at a range of spatial and temporal scales due to man-made and natural causes and the complex interaction of the two. In 1985 cyclone Sandy caused a 183 km2 loss of seagrass in the Gulf of Carpentaria, which was 20 per cent of the seagrasses of the Gulf. After 12 years, much of the area had recovered to pre-cyclone levels but there is still a large area (20 km2) devoid of seagrass that previously supported seagrass communities (Poiner et.al. 1993). In 1992-93 an estimated 900 km2 of seagrass in Hervey Bay in Queensland disappeared. The cause of this loss is not known although it is thought that high turbidities, resulting from flooding of the Mary and Burrum Rivers, and run off from cyclone Fran three weeks later, were responsible (Preen et.al. 1993). Similarly 1199 km2 of seagrass in the Torres Strait was lost probably due to high turbidities, resulting from flooding of the Mai River (Long et.al. 1997).
Seagrass declines in Moreton Bay have been attributed to the deterioration of water quality from urbanisation, industrialisation and increased land use resulting in increases in nutrient loading, sedimentation, influx of contaminants and toxins or other detrimental effects on seagrass communities (Kirkman 1978, Hyland et.al. 1989, Abal and Dennison 1996).
Outbreaks of Lyngbya majuscula, a cynobacterium commonly known as mermaidís hair or fireweed, can have major impacts on ecosystem health. In bloom conditions Lyngbya forms dense mats that cover the sea floor, smothering underlying seagrass meadows.
Seagrass systems do not readily recover. The plants require appropriate water quality and special conditions in the substrate that are not present in disturbed or most sandy substrates. Consequently, once an area has been denuded of seagrass, it may not recover or may take a long time.

 
   
   
   
   
   

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